[1] It was originally described as being a trilobite-like arthropod, though the majority of experts now place it within the Proarticulata as a close relative of the much larger Yorgia.

On average, P. sigillum had at least 5 pairs of segments, with each unit becoming progressively larger as they approach the cephalon-like head.

Fedokin (1992) suggested that P. sigillum should become a synonym of Spriggina, while others have stated that the animal shares more in common with Dickinsonia brachina.

[7] P. sigillum possessed a head shield that paired a branching pair of ribs with the ribs of the organism tapering towards their end and as they get further from the head shield, they point towards the end of the animal;[5] with Glaessner and Wade concluding that the segments (or lobes) increased in size during growth of Praecambridium.

[8] The sculpture of the head shield of Praecambridium siggilum has been proposed as being the expression of an underlying digestive/distribution system which is also seen in agnostid trilobites.